1. Technical Field
The present disclosure relates to a semiconductor light source drive device that supplies a semiconductor light source with a drive current modulated by a high-speed pulse width.
2. Description of the Related Art
Patent literature 1 discloses a circuit for driving a light-emitting element (e.g., an LED) that outputs a constant level of pulse current limitedly affected by fluctuation of temperature and power supply voltage, and variations of elements.
The driving circuit includes a switch that turns on and off power supplied from a switching power source to a drive target; a detecting means that detects a current having flown to the drive target and outputs a detection signal corresponding to the detection result; and an error signal generation means that generates an error signal corresponding to an error between the detection signal output from the detecting means and a target signal. The driving circuit further includes a signal retaining means, which, when the switch is on, averages error signals generated by the error signal generation means; when the switch turns from on to off, retains the averaged error signal; and when the switch turns from off to on, starts averaging error signals with the retained signal level being the initial level. When the switch is off, the driving circuit stops supplying power from the switching power source to the drive target. When the switch is on, the driving circuit controls power supplied from the switching power source to the drive target in response to the error signal averaged by the signal retaining means.
This configuration provides a drive circuit that outputs a constant level of pulse current limitedly affected by fluctuation of temperature and power supply voltage, and manufacturing variations of elements.